The overall objectives of the project are to determine the interactions among monoaminergic, cholinergic and amino acid transmitter systems in the CNS. The interactions of multiple neuronal pathways are the fundamental way by which the nervous system processes information. Since neurons interact by a chemically mediated release process, we propose to assess the neuronal inter-relationships by measuring the release of endogenous norepinephrine (NE), dopamine (DA), serotonin (5-HT), GABA, glutamate and aspartate under controlled in vitro conditions in the cerebral cortex, hypothalamus and nucleus accumbens of the rat. Slices or synaptosomes will be prepared by standard procedures and then suspended in a bed of Sephadex for support in polypropylene columns while superfusing with submaximal stimulating concentrations of K+. The effects of individually adding NE, DA and 5-HT to this stimulating medium on the release of GABA, aspartate, glutamate and the monoamines will be determined. In addition, the effects of GABA, aspartate and glutamate on the release of NE, DA, 5-HT and amino acid transmitters will be determined. Also, the effects of carbachol (a nicotinic and muscarinic cholinergic agonist) on the release of the monoamines and putative amino acid transmitters will be studied. Selective antagonists will be used to assess specificity of action. These data should provide more detailed information on inter-neuronal relationships and axo-axonal synapses of monoaminergic, cholinergic and amino acid transmitter systems in specific regions of the CNS of the rat.